Phylogeography of the pallid kangaroo mouse, Microdipodops pallidus: a sand-obligate endemic of the Great Basin, western North America

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Kangaroo mice, genus Microdipodops Merriam, are endemic to the Great Basin and include two species: M. pallidus Merriam and M. megacephalus Merriam. The pallid kangaroo mouse, M. pallidus, is a sand-obligate desert rodent. Working in the sandy habitats of the Great Basin Desert region, especially the of the Lahontan Trough and of south-central Nevada, the authors sought to identify the species’ current geographical distribution and formulate a phylogeographical hypothesis for the taxon. In addition, they tested for orientation patterns in haplotype sharing for evidence of past episodes of movement and gene flow. Mitochondrial DNA sequence data from portions of three genes were obtained from 98 individuals of M. pallidus, representing 27 general localities sampled throughout its geographical range. Molecular sequence data were analyzed using neighbor-joining, maximum-parsimony, maximum-likelihood, and Bayesian methods of phylogenetic inference. Directional analysis of phylogeographical patterns, a novel method, was used to examine angular measurements of haplotype sharing between pairs of localities to detect and quantify historical events pertaining to movement patterns and gene flow. Collecting activities showed that M. pallidus is a rather rare rodent (mean trapping success was 2.88%) and its distribution has changed little from that determined 75 years ago. Two principal phylogroups, distributed as eastern and western moieties, are evident from the phylogenetic analyses (mean sequence divergence for cytochrome b is c. 8%). The western clade shows little phylogenetic structure and seems to represent a large polytomy. In the eastern clade, however, three subgroups are recognized. Nine of the 42 unique composite haplotypes are present at two or more localities and are used for the orientation analyses. Axial data from haplotype sharing between pairwise localities show significant, non-random angular patterns: a north-west to south-east orientation in the western clade, and a north-east to south-west directional pattern in the eastern clade. The geographical range of M. pallidus seems to be remarkably stable in historical times and does not show a northward (or elevationally upward) movement trend, as has been reported for some other kinds of organism in response to global climate change. The eastern and western clades are likely to represent morphologically cryptic species. Estimated times of divergence of the principal clades of M. pallidus (4.38 Ma) and between M. pallidus and M. megacephalus (8.1 Ma; data from a related study) indicate that kangaroo mice diverged much earlier than thought previously. The phylogeographical patterns described here may serve as a model for other sand-obligate members of the Great Basin Desert biota.

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ELECTRONIC FILE - Zoology

SWAP (2/19/2016) citation:
Hafner JC, Upham NS, Reddington E, Torres CW. 2008. Phylogeography of the pallid kangaroo mouse, Microdipodops pallidus: a sand-obligate endemic of the Great Basin, western North America. [accessed 2016 Feb 03]; Journal of Biogeography. 35(11):2102–2118. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2699.2008.01942.x/epdf